Nickel block of three cloned T-type calcium channels:: Low concentrations selectively block α1H
Nickel block of three cloned T-type calcium channels:: Low concentrations selectively block α1H
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DOI：
10.1016/s0006-3495(99)77134-1
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发表时间：
1999-12-01
影响因子：
3.4
通讯作者：
Perez-Reyes, E
中科院分区：
文献类型：
--
作者：
Lee, JH;Gomora, JC;Perez-Reyes, E
镍被认为是低电压激活的T型钙通道的选择性阻滞剂。然而，对克隆的高压激活的钙通道的研究表明，一些亚型，如α1E，也被低摩尔浓度的NiCl2阻断。不同天然的T型电流对Ni2+的敏感性有相当大的差异，这导致了可能存在不止一个T型通道的假设。我们克隆了三个新的钙通道，即G、I-I和II，它们的电流几乎与天然T-型通道的生物物理特性相同，从而证实了这一假设的一部分。在这项研究中，我们检测了这些克隆的T型通道在非洲爪哇卵母细胞和HEK-293细胞(10 mM Ba2+)中的表达。只有α-1H电流对低微摩尔浓度(IC50=13mM)敏感。需要更高的浓度才能半阻断阿尔法1I(216微米)和阿尔法1G电流(250微米)。镍阻挡随测试电位不同而不同，在-30 mV以上阻挡较少。通过T通道的外向电流被阻断得更少。我们证明了去极化可以解除通道的阻塞，并且这可以在没有渗透离子的情况下发生。我们的结论是，Ni2+只是α1H电流的选择性阻滞剂，阻断α1G和α1I所需的浓度也会影响高压激活的钙电流。
Nickel has been proposed to be a selective blocker of low-voltage-activated, T-type calcium channels. However, studies on cloned high-voltage-activated Ca2+ channels indicated that some subtypes, such as alpha 1E, are also blocked by low micromolar concentrations of NiCl2. There are considerable differences in the sensitivity to Ni2+ among native T-type currents, leading to the hypothesis that there may be more than one T-type channel. We confirmed part of this hypothesis by cloning three novel Ca2+ channels, orlG, I-I, and II whose currents are nearly identical to the biophysical properties of native T-type channels. In this study we examined the nickel block of these cloned-T-type channels expressed in both Xenopus oocytes and HEK-293 cells (10 mM Ba2+). Only alpha 1H currents were sensitive to low micromolar concentrations (IC50 = 13 mu M). Much higher concentrations were required to half-block alpha 1I (216 mu M) and alpha 1G currents(250 mu M). Nickel block varied with the test potential, with less block at potentials above -30 mV. Outward currents through the T channels were blocked even less. We show that depolarizations can unblock the channel and that this can occur in the absence of permeating ions. We conclude that Ni2+ is only a selective blocker of alpha 1H currents and that the concentrations required to block alpha 1G and alpha 1I will also affect high-voltage-activated calcium currents.